Methods of selective oxidation conditions for dielectric conditioning

ABSTRACT

A method for conditioning or repairing a dielectric structure of a semiconductor device structure with selectivity over an adjacent conductive or semiconductive structure of the semiconductor device structure, such as a capacitor dielectric and an adjacent bottom electrode of the capacitor. The method includes exposing the dielectric structure and at least an adjacent surface of the conductive or semiconductive structure to an oxidizing atmosphere that includes at least one oxidant and hydrogen species. The at least one hydrogen species adsorbs to a surface of the conductive or semiconductive structure so as to substantially prevent passage of the at least one oxidant into or through the conductive or semiconductive structure. The oxidant oxidizes or repairs voids or other defects that may be present in the dielectric structure. Semiconductor device structures fabricated by employing the method are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of application Ser. No.09/652,751, filed Aug. 31, 2000, pending.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to methods for conditioning orreoxidizing dielectric layers of semiconductor device structures withoutsubstantially oxidizing conductive or semiconductive structures adjacentthereto. Particularly, the present invention relates to methods forconditioning or reoxidizing capacitor dielectric layers withoutsubstantially oxidizing the materials of adjacent capacitor electrodes.

[0004] 2. State of the Art

[0005] In state of the art semiconductor devices, capacitors typicallyinclude a bottom electrode having a relatively large surface area, adielectric layer formed over the bottom electrode, and an upperelectrode formed over the dielectric layer. FIG. 1 illustrates anexemplary semiconductor device capacitor 10, formed over and in contactwith an active device region 14 of a semiconductor substrate 12.Capacitor 10 includes a bottom electrode 16 formed over and in contactwith the active device region 14, a dielectric layer 18 positioned overthe bottom electrode 16, and an upper electrode 20 positioned over thedielectric layer 18.

[0006] After the bottom electrode 16 and capacitor dielectric 18 layersof the capacitor 10 have been formed, these layers and various otherstructures may be patterned in accordance with a particular integratedcircuit design. Among the processes that are employed to effect suchpatterning, dry etch processes, including plasma etches, may be used.Nonetheless, plasma etches tend to cause considerable damage to thedielectric layer 18. Such damage may result regardless of efforts tooptimize etch selectivity and optical end point measurement techniques.Aside from physical thinning and possibly creating voids or otherdefects in the dielectric layer 18, plasma etching may damage oxidebonds, creating charge trap sites, such as dangling silicon bonds whenpolysilicon is employed as the bottom electrode 16. The presence ofvoids, other defects, and charge trap sites in the dielectric layer 18may diminish the desired dielectric properties of the dielectric layer18 and, thus, the capacitance of the finished capacitor 10. Accordingly,this damage should be repaired to improve the quality and lifeexpectancy of the dielectric layer 18 and of the capacitor 10. Anoxidation or reoxidation step is commonly used to repair the dielectriclayers.

[0007] As the dimensions of semiconductor device structures, includingthe thicknesses of capacitor dielectric layers, are ever decreasing,materials with greater dielectric constants are being used withincreased frequency. These dielectric materials, like tantalum pentoxide(Ta₂O₅) and barium strontium titanate (BST), are typically deposited andannealed at temperatures near 600° C. and in the presence of high oxygenpartial pressure. Nonetheless, voids, defects, and charge trap sites maybe present in the extremely thin capacitor dielectric layers formed withsuch materials. Thus, conditioning by oxidizing or reoxidizing ofdielectric layers formed with these materials may be necessary tofabricate a capacitor with the desired electrical properties.Conditioning can involve wet oxidation at temperatures above 900° C. fora relatively long period of time (e.g., up to about 30 minutes). Duringoxidation at such high temperatures, the dielectric layer 18 istypically thickened.

[0008] Unfortunately, conditions during oxidation also result inoxidation of the underlying materials, including portions of the bottomelectrode 16. The longer the oxidation process and the higher thetemperature, the more metal, metal nitride and/or silicide are consumed.Such oxidation of the bottom electrode 16 further effectively thickensthe dielectric layer 18, often undesirably changing the capacitance ofthe capacitor 10. In addition, some metals, such as tungsten, are soreadily oxidized in such processes that these metals are effectivelyrendered impractical for use as the bottom electrodes in capacitors.

[0009] One commonly utilized solution to the problem of oxidizing abottom electrode of a capacitor structure during conditioning of anoverlying dielectric layer is to provide an oxidation barrier layerbetween the bottom electrode and the overlying dielectric layer.However, there are a limited number of oxidation barrier materials whichare conductive.

[0010] Processes are also known for oxidizing silicon with selectivityover adjacent structures formed from tungsten or tungsten nitride.

[0011] The inventors are not aware of any art that teaches conditioningof a dielectric layer of a capacitor structure by selective oxidizationof the dielectric layer without substantially oxidizing an adjacent,underlying bottom electrode layer.

BRIEF SUMMARY OF THE INVENTION

[0012] In accordance with one aspect of the present invention, a methodis provided for selectively oxidizing a dielectric layer of a structurewithout substantially oxidizing an adjacent conductive or semiconductivelayer or structure. The inventive method includes exposing at least aportion of the dielectric oxidizing the electronic device by exposingthe layer or structure to a selective oxidation atmosphere. Theselective oxidation growth ambient selectively oxidizes or reoxidizesthe dielectric layer or structure without the bottom electrode.

[0013] Another embodiment of the method of the present inventionprovides a method for conditioning a dielectric layer or structure byrepairing voids or other defects in the dielectric layer or structure.Such a method includes forming a dielectric layer above a bottomelectrode of a capacitor structure, exposing the bottom electrode tohydrogen species, and oxidizing the dielectric layer. The adsorption ofthe hydrogen species to a surface of the bottom electrode, substantiallyprevents oxidation of the bottom electrode, making the oxidation processselective for the dielectric layer.

[0014] A further embodiment of the method of the present inventionincludes forming a capacitor structure, which method includes a bottomelectrode, forming at least one dielectric layer above the bottomelectrode, adsorbing a hydrogen species on a surface of the bottomelectrode, and oxidizing said at least one dielectric layer. Again, theadsorption of hydrogen species to a surface of the bottom electrodemakes oxidation of the dielectric layer selective for the dielectriclayer.

[0015] The present invention also includes a semiconductor devicestructure with a conductive or semiconductive structure adjacent to thedielectric structure. A hydrogen species is at least adsorbed to aportion of a surface of the conductive or semiconductive structure incontact with the dielectric structure. In an intermediate state, thedielectric structure may include voids, other defects, or charge traps.In a subsequently formed intermediate structure, the dielectricstructure of the semiconductor device structure may be substantiallyfree of voids, other defects, and charge traps while the hydrogenspecies remain present at least at an interface between the dielectricstructure and the adjacent conductive or semiconductive structure.

[0016] Other features and advantages of the present invention willbecome apparent to those of skill in the art through a consideration ofthe ensuing description, the accompanying drawings, and the appendedclaims.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0017] In the drawings, which illustrate exemplary embodiments of thepresent invention:

[0018]FIG. 1 is a cross-sectional representation of a conventionalsemiconductor device capacitor structure; and

[0019]FIG. 2 is a cross-sectional schematic representation of use of themethod of the present invention to selectively oxidize a dielectricstructure of a semiconductor device structure without substantiallyoxidizing an adjacent conductive or semiconductive structure.

DETAILED DESCRIPTION OF THE INVENTION

[0020] The illustrated embodiments provide a method of minimizingoxidation of conductors in integrated circuits. Although the illustratedand disclosed embodiment is described in terms of a method forconditioning a capacitor structure for use in a semiconductor device,the skilled artisan will readily appreciate that the methods describedherein will also have application to methods for conditioning orselectively oxidizing other types of dielectric structures withoutsubstantially oxidizing the material or materials of conductive orsemiconductive structures adjacent to the dielectric structures.

[0021] With reference to FIG. 2, an intermediate capacitor structure 10′is illustrated. Structure 10′ is part of a semiconductor devicestructure that includes a semiconductor substrate 12′ with conductivelydoped active device regions 14′ formed therein. Capacitor structure 10′includes a bottom electrode 16′ partially formed over and in electricalcommunication with an active device region 14′. Capacitor structure 10′also includes a dielectric layer 18′ formed over and in contact with thebottom electrode 16′. The capacitor structure 10′ may also includeadditional conductive or insulative layers (not shown).

[0022] Bottom electrode 16′ of capacitor structure 10′ may be formedfrom any conductive material that is suitable for use in a capacitor ofa semiconductor device. In effecting the selective oxidation method ofthe present invention, it is preferred that bottom electrode 16′ beformed from a conductive material such as ruthenium, ruthenium oxide,platinum, titanium nitride, tungsten, tungsten nitride, cobalt, orpolysilicon. Alternatively, bottom electrode 16′ may be formed from anyconductive, metallic catalyst for ammonia combustion.

[0023] The dielectric layer 18′ of capacitor structure 10′ may be formedfrom any dielectric material suitable for use in capacitors ofsemiconductor devices. Examples of high dielectric constant materialsthat are useful in forming dielectric layer 18′ include, withoutlimitation, tantalum pentoxide (Ta₂O₅), barium strontium titanate (BST),strontium titanate (ST), barium titanate (BT), lead zirconium titanate(PZT), and strontium bismuth tantalate (SBT). Dielectric layer 18′ mayalso be formed from one or more silicon nitrides or silicon oxides.

[0024] As the dielectric layer 18′ of the capacitor structure 10′ mayinclude voids, other defects, or charge trap sites that may reduce thedielectric properties of dielectric layer 18′ and, thus, undesirablyaffect the capacitance of a capacitor including the dielectric layer18′, dielectric layer 18′ is conditioned or repaired by oxidizing orreoxidizing the same. While conditioning or repairing a dielectric layer18′ in accordance with teachings of the present invention, an adjacentconductive or semiconductive structure, such as the bottom electrode 16′of capacitor structure 10′, is not substantially oxidized and oxidantsmay actually be substantially prevented from traveling through theadjacent conductive or semiconductive structure.

[0025] A selective oxidation method according to the present inventionincludes exposing at least a portion of the dielectric layer 18′ to anoxidizing atmosphere 22 that includes an oxidant and hydrogen species.The oxidizing atmosphere 22 may also include nitrogen species. While thehydrogen species 24 permeates or at least adsorbs to a surface of anadjacent conductive or semiconductive structure, such as the bottomelectrode 16′, so as to reduce and, thereby prevent, oxidation of thematerial of the adjacent conductive or semiconductive structure, theoxidant oxidizes the dielectric layer 18′. Accordingly, an oxidizingatmosphere 22 incorporating teachings of the present invention is saidto selectively oxidize the dielectric layer 18′.

[0026] Exemplary oxidants that may be used in the oxidizing atmosphere22 include, without limitation, water (H₂O), hydrogen peroxide (H₂O₂),carbon monoxide (CO), carbon dioxide (CO₂), nitric oxide (NO), andnitrous oxide (N₂O). It is preferred that the oxidant in the oxidizingatmosphere 22 be relatively nonreactive with the hydrogen species 24. Asmolecular oxygen (O₂) may react with the hydrogen species 24, it ispreferred that molecular oxygen not be used as the oxidant of theoxidizing atmosphere 22.

[0027] The hydrogen species 24 of the oxidizing atmosphere 22 may bederived from ammonia (NH₃). It is preferred that ammonia be used in theoxidizing atmosphere 22 as a source for either the hydrogen species 24or the nitrogen species when a conductive structure adjacent theconditioned dielectric layer 18′ is formed from a conductive, metalliccatalyst for ammonia combustion. A skilled artisan will readilyrecognize alternative species that may adsorb to the surface of aconductive or semiconductive structure adjacent a dielectric structureto be conditioned. Accordingly, the use of such alternative species inan oxidizing atmosphere 22 are also within the scope of the presentinvention.

[0028] In addition to preventing oxidation of a conductive orsemiconductive structure adjacent to a conditioned dielectric structure,the hydrogen species may also prevent oxidants from passing through theconductive or semiconductive structure and, thus, from oxidizing otherstructures, such as active device region 14′, opposite the conductive orsemiconductive structure from the conditioned dielectric structure.

[0029] In effecting the method of the present invention, the dielectriclayer 18′ or the portion thereof to be conditioned or reoxidized isexposed to an oxidizing atmosphere 22 according to the present inventionin the presence of heat. For example, rapid thermal processing (RTP) maybe employed to condition or repair the dielectric layer 18′. Exemplaryrapid thermal process parameters include temperatures of from about 800°C. to about 1,100° C. and durations of about 20 seconds to about 4minutes for a longer period. As another example of the manner in whichselective oxidation may be effected in accordance with teachings of thepresent invention, an atmospheric furnace may be employed. When anatmospheric furnace is employed to effect the methods of the presentinvention, the oxidizing atmosphere 22, and at least the portion of thedielectric layer 18′ to be conditioned or repaired, is exposed to atemperature of from about 650° C. to about 950° C. for up to about 3hours.

[0030] As an example of the manner in which the oxidizing atmosphere 22may be introduced into the presence of the dielectric layer, thevolumetric ratio of the hydrogen-containing species (e.g., H₂ or NH₃) tothe oxidant may be about 1:1 to about 200:1 and is preferably about 2:1to about 10:1. The hydrogen species flow rates may be between about1,000 sccm and 10,000 sccm and, preferably, between about 2,000 sccm and7,000 sccm. Water vapor may be flowed at a rate of between about 50 sccmand 2,000 sccm. The oxidizing atmosphere 22 may have a pressure of about250 mTorr to about 50 atm. and, preferably, of between about 350 Torrand 1,000 Torr.

[0031] Although the foregoing description contains many specifics, theseshould not be construed as limiting the scope of the present invention,but merely as providing illustrations of some of the presently preferredembodiments. Similarly, other embodiments of the invention may bedevised which do not depart from the spirit or scope of the presentinvention. Features from different embodiments may be employed incombination. The scope of the invention is, therefore, indicated andlimited only by the appended claims and their legal equivalents, ratherthan by the foregoing description. All additions, deletions, andmodifications to the invention as disclosed herein which fall within themeaning and scope of the claims are to be embraced thereby.

What is claimed is:
 1. A method for selectively oxidizing a dielectriclayer without substantially oxidizing an adjacent conductive orsemiconductive material underlying said dielectric layer by exposing atleast said dielectric layer and an adjacent surface of said conductiveor semiconductive material to an oxidizing atmosphere comprising anoxidant and at least one hydrogen species.
 2. The method of claim 1,wherein said exposing further comprises exposing at least saiddielectric layer and said adjacent surface of said conductive orsemiconductive material to an oxidizing atmosphere including H₂O andsaid at least one hydrogen species.
 3. The method of claim 2, whereinsaid exposing comprises exposing at least said dielectric layer and saidadjacent surface of said conductive or semiconductive material to saidoxidizing atmosphere, which further includes nitrogen.
 4. The method ofclaim 2, wherein said exposing comprises exposing at least saiddielectric layer and said adjacent surface of said conductive orsemiconductive material to said oxidizing atmosphere, wherein said atleast one hydrogen species of said oxidizing atmosphere is at leastpartially derived from ammonia.
 5. The method of claim 1, wherein saidexposing comprises exposing at least said dielectric layer and saidadjacent surface of said conductive or semiconductive material to anoxidizing atmosphere comprising an oxidant and said at least onehydrogen species.
 6. The method of claim 5, wherein said exposingcomprises exposing at least said dielectric layer and said adjacentsurface of said conductive or semiconductive material to said oxidizingatmosphere, with said oxidant of said oxidizing atmosphere comprising atleast one of CO, CO₂, NO, N₂O, H₂O₂, and H₂O.
 7. The method of claim 5,wherein said exposing comprises exposing at least said dielectric layerand said adjacent surface of said conductive or semiconductive materialto said oxidizing atmosphere, wherein said at least one hydrogen speciesof said oxidizing atmosphere is at least partially derived from ammonia.8. The method of claim 1, wherein said selectively oxidizing saiddielectric layer comprises selectively oxidizing a dielectric layerincluding at least one of Ta₂O₅, barium strontium titanate, a siliconnitride, and a silicon oxide.
 9. The method of claim 1, wherein saidselectively oxidizing said dielectric layer comprises selectivelyoxidizing a dielectric layer overlying a conductive or semiconductivematerial comprising a metallic catalyst for ammonia combustion.
 10. Themethod of claim 1, wherein said selectively oxidizing said dielectriclayer comprises selectively oxidizing a dielectric layer overlying aconductive or semiconductive material comprising at least one ofruthenium, ruthenium oxide, platinum, titanium nitride, tungsten,tungsten nitride, polysilicon, and cobalt.
 11. The method of claim 2,wherein said exposing comprises adsorbing said at least one hydrogenspecies to said adjacent surface of said conductive or semiconductivematerial.
 12. The method of claim 11, wherein said adsorbing comprisessubstantially preventing an oxidant from passing through said conductiveor semiconductive material.
 13. The method of claim 1, wherein saidoxidant and said at least one hydrogen species are provided in avolumetric ratio of between about 1:1 to about 1:200.
 14. The method ofclaim 13, wherein said oxidant and said at least one hydrogen speciesare provided in a volumetric ratio of between about 1:2 to about 1:10.15. A method for forming a semiconductor device, comprising: forming alayer of conductive or semiconductive material; forming at least onedielectric layer adjacent said layer of conductive or semiconductivematerial; adsorbing at least one hydrogen species onto at least asurface of said layer of conductive or semiconductive material; andoxidizing said at least one dielectric layer in an oxidizing atmospherecomprising an oxidant during or after said adsorbing.
 16. The method ofclaim 15, wherein said forming said layer of conductive orsemiconductive material comprises forming said layer of conductive orsemiconductive material with a metallic catalyst for ammonia combustion.17. The method of claim 15, wherein said forming said layer ofconductive or semiconductive material comprises forming said layer ofconductive or semiconductive material with at least one of ruthenium,ruthenium oxide, platinum, titanium nitride, tungsten, tungsten nitride,polysilicon, and cobalt.
 18. The method of claim 15, wherein saidforming said at least one dielectric layer comprises forming said atleast one dielectric layer with at least one of Ta₂O₅, barium strontiumtitanate, a silicon nitride, and a silicon oxide.
 19. The method ofclaim 15, further comprising generating said at least one hydrogenspecies.
 20. The method of claim 19, wherein said generating said atleast one hydrogen species comprises generating said at least onehydrogen species from ammonia.
 21. The method of claim 15, wherein saidoxidizing comprises exposing at least said at least one dielectric layerto at least one of H₂O, H₂O₂, CO, CO₂, NO, and N₂O.
 22. The method ofclaim 15, further comprising exposing at least said at least onedielectric layer to nitrogen species.
 23. The method of claim 15,wherein said oxidant and said at least one hydrogen species are providedin a volumetric ratio of between about 1:1 to about 1:200.
 24. Themethod of claim 15, wherein said oxidant and said at least one hydrogenspecies are provided in a volumetric ratio of between about 1:2 to about1:10.
 25. A method of conditioning a dielectric layer comprising:providing a structure comprising a conductive or semiconductivematerial; adhereing a hydrogen species to a surface of said conductiveor semiconductive material; forming a dielectric layer adjacent saidconductive or semiconductive material after said adhereing; and exposingat least said dielectric layer to an oxidizing atmosphere comprising anoxidant after said forming.
 26. The method of claim 25, wherein saidadhereing further comprises at least partially generating said hydrogenspecies from ammonia.
 27. The method of claim 25, wherein said exposingcomprises exposing at least said dielectric layer to said oxidizingatmosphere comprises exposing said dielectric layer to an oxidantcomprising at least one of CO, CO₂, NO, N₂O, H₂O₂, and H₂O.
 28. Themethod of claim 25, wherein said forming said dielectric layer comprisesforming a dielectric layer including at least one of Ta₂O₅, bariumstrontium titanate, a silicon nitride, and a silicon oxide.
 29. Themethod of claim 25, wherein said forming said dielectric layer comprisesforming a dielectric layer overlying a conductive or semiconductivematerial comprising a metallic catalyst for ammonia combustion.
 30. Themethod of claim 25, wherein said forming said dielectric layer comprisesforming a dielectric layer overlying a conductive or semiconductivematerial comprising at least one of ruthenium, ruthenium oxide,platinum, titanium nitride, tungsten, tungsten nitride, polysilicon, andcobalt.
 31. The method of claim 25, wherein said adhereing comprisessubstantially preventing an oxidant from passing through said conductiveor semiconductive material.
 32. The method of claim 25, wherein saidoxidant and said hydrogen species are provided in a volumetric ratio ofbetween about 1:1 to about 1:200.
 33. The method of claim 32, whereinsaid oxidant and said hydrogen species are provided in a volumetricratio of between about 1:2 to about 1:10.
 34. A method of preventingoxidants from passing through a conductive or semiconductive structureduring oxidation of an adjacent dielectric structure, comprising:adsorbing a hydrogen species to a surface of a conductive orsemiconductive structure during or prior to exposing an adjacentdielectric structure to an oxidizing atmosphere comprising at least oneoxidant.
 35. The method of claim 34, wherein said adsorbing comprisinggenerating said hydrogen species at least partially from ammonia. 36.The method of claim 34, wherein said adsorbing comprises generating saidhydrogen species at least partially from a nitrogen containing species.37. The method of claim 34, further comprising forming said conductiveor semiconductive structure from a metallic catalyst for ammoniacombustion.
 38. The method of claim 34, further comprising forming saidconductive or semiconductive structure from at least one of ruthenium,ruthenium oxide, platinum, titanium nitride, tungsten, tungsten nitride,polysilicon, and cobalt.
 39. The method of claim 34, further comprisingforming said adjacent dielectric structure from at least one of Ta₂O₅,barium strontium titanate, a silicon nitride, and a silicon oxide. 40.The method of claim 34, wherein said oxidizing comprises exposing atleast said dielectric structure to at least one of H₂O, H₂O₂, CO, CO₂,NO, and N₂O.
 41. The method of claim 34, wherein said oxidant and saidhydrogen species are provided in a volumetric ratio of between about 1:1to about 1:200.
 42. The method of claim 34, wherein said oxidant andsaid hydrogen species are provided in a volumetric ratio of betweenabout 1:2 to about 1:10.
 43. A method for increasing the confluency of acapacitor dielectric, comprising: providing a semiconductor devicestructure including a capacitor electrode and a capacitor dielectriclocated over said capacitor electrode, said capacitor dielectricincluding at least one void or defect therein; and exposing at leastsaid capacitor dielectric and an adjacent surface of said capacitorelectrode to an oxidizing atmosphere comprising at least an oxidant andat least one hydrogen species.
 44. The method of claim 43, wherein saidproviding comprises providing said semiconductor device structure withsaid capacitor electrode comprising a metallic catalyst for ammoniacombustion.
 45. The method of claim 43, wherein said providing saidsemiconductor device structure comprises providing a semiconductordevice structure with said capacitor electrode comprising at least oneof ruthenium, ruthenium oxide, platinum, titanium nitride, tungsten,tungsten nitride, polysilicon, and cobalt.
 46. The method of claim 43,wherein said providing said semiconductor device structure comprisesproviding a semiconductor device structure with said capacitordielectric comprising at least one of Ta₂O₅, barium strontium titanate,a silicon nitride, and a silicon oxide.
 47. The method of claim 43,wherein said exposing comprises exposing at least said capacitordielectric and said adjacent surface of said capacitor electrode to saidoxidizing atmosphere, with said oxidant comprising H₂O.
 48. The methodof claim 43, wherein said exposing comprises exposing at least saidcapacitor dielectric and said adjacent surface of said capacitorelectrode to said oxidizing atmosphere, with said oxidant comprising atleast one of H₂O₂, CO, CO₂, NO, and N₂O.
 49. The method of claim 43,wherein said exposing comprises exposing at least said capacitordielectric and said adjacent surface of said capacitor electrode to saidoxidizing atmosphere, with said at least one hydrogen species beingderived from ammonia.
 50. The method of claim 43, wherein said exposingcomprises exposing at least said capacitor dielectric and said adjacentsurface of said capacitor electrode to said oxidizing atmosphere, withsaid oxidizing atmosphere further including nitrogen.
 51. The method ofclaim 43, wherein said exposing comprises adsorbing said at least onehydrogen species to said adjacent surface of said capacitor electrode.52. The method of claim 51, wherein said adsorbing comprisessubstantially preventing said oxidant from passing through saidcapacitor electrode.